Conventionally, seat belts are provided as the means for preventing passengers from moving forward inertially upon an abrupt vehicle deceleration. Nevertheless, there has been the problem that they fail to function effectively when the passengers' rear end sinks into the seat cushions and moves forward as well. Description will be given with reference to FIGS. 34A to 34C. If a frontal crash occurs when a passenger 100 is sitting on a seat cushion 101 properly and wearing a seat belt 102 as shown in FIG. 34A, the passenger 100 sinks and moves forward as shown in FIG. 34B due to an inertial force. Then, at a maximum deceleration, the rear end of the passenger 100 sinks into the seat cushion 101 and moves over to the front end thereof as shown in FIG. 34C. This is sometimes referred to as submarine phenomenon.
To prevent the rear end of the passenger 100 from moving to the front of the seat cushion 101 thus, there has been proposed as shown in FIG. 35 that the seat cushion 101 be provided with a cross member 103 such as a pipe across the lateral width direction of the seat cushion 101, in a position in front of the rear end of the passenger 100 in a proper seating state. Consequently, by the cross member 103 catching the rear end of the passenger 100, the cross member 103 can be deformed to absorb the impact and suppress the forward movement.
When the cross member 103 such as a pipe is arranged in the front portion of the seat cushion 101, however, there occurs the problem that the seating comfort of the passenger 100 deteriorates to hamper driving comfort. On the other hand, when the position of arrangement of the cross member 103 is lowered to a position having no impact on the seating comfort, there arises the problem that the effect of preventing the forward movement of the passenger 100 is no longer obtained.
Then, as shown in FIGS. 36A and 36B, there has been proposed one in which: under normal conditions, the cross member 103 is situated in a lower position as shown in FIG. 36A; and upon a crash, driving means 105 such as an inflator is activated to lift up the cross member 103 as shown in FIG. 36B via interlocking means 104 such as a link mechanism if needed. Technical means of this type have been disclosed, for example, in Japanese Patent Laid-Open Publication No. Hei 5-238297, Japanese Patent Laid-Open Publication No. Hei 7-81466, and so on. In addition, Japanese Utility Model Laid-Open Publication No. Hei 7-5898 has disclosed one in which the front portion of the seat cushion itself is lifted upon a crash.
Moreover, the present applicant has proposed in Japanese Patent Application No. 2000-38402 a configuration in which a catch member extending horizontally is arranged inside a seat cushion as supported by a guide so as to be vertically movable, and means is provided for urging the catch member upward. The catch member smoothly moves downward when a load acts thereon from above. The catch member comes into engagement with a front side edge of the guide and is inhibited from moving downward when a load acts thereon from behind. The forward movement of the passenger is caught by this catch member.
The configuration shown in FIGS. 36A and 36B and the configurations disclosed in the foregoing individual publications, however, require a mechanism for lifting the cross member 103 forcibly at necessary time, driving means 104 and 105 thereof, and the like. This gives rise to the problem that the apparatus becomes complicated with an increase in cost and with an increase in weight.
Meanwhile, in the configuration disclosed in Japanese Patent Application No. 2000-38402 described above, the configuration is simple and the seating comfort at the time of seating is acceptable. However, when the passenger's rear end moves forward upon a frontal crash, the catch member may be diverted down by a downward component of the load acting on the catch member. This means the problem that the stable effect of preventing the passenger's forward movement cannot be obtained with stability.
Moreover, in recent years, it is legally obligatory in many countries to use child seats when children are on vehicles. Then, various systems have been proposed as the system for installing a child seat on a seat cushion 101. For example, in a method, the child seat is placed on the seat cushion 101 and fixed by using a seat belt 102. The fixing method, however, is troublesome and requires skills to establish a highly reliable state of fixing quickly. This also means the problem that there can occur insecure fixing.
Among the other systems proposed is one in which an anchor 109 is attached to a body frame 108 so as to lie between the rear end of the seat cushion 101 and the bottom end of a seat back 107, and a to-be-engaged portion 111 capable of being engaged with the anchor 109 is arranged on a rear bottom portion of the child seat 110 as shown in FIG. 37. The child seat 110 is placed on the seat cushion 101 and fixed by engaging the to-be-engaged portion 111 with the anchor 109. This system is prescribed by ISO standards and is referred to as ISO system.
In this system, there is no possibility that the child seat 100 is thrown forward upon an abrupt deceleration, whereas the child seat 100 undergoes forward rotation moment about the engaging point between the to-be-engaged portion 111 and the anchor 109 as shown by the arrow. Due to the cushioning of the seat cushion 101, as shown by the imaginary lines in FIG. 37, the front portion of the seat cushion 101 easily yields to swing the child seat 100 forward. This has produced the problem that greater movement of the child's head can hinder sufficient safety being secured.
In view of this, methods have been proposed such that a hard pad or metal cross member 112 is in the front portion of the seat cushion 101 as shown in FIG. 38A, that support legs 113 are arranged between the front bottom portion of the child seat 100 and the floor surface of the cabin as shown in FIG. 38B, and that the rear top portion of the child seat 100 and a hook 114 arranged on the body side are coupled with a coupling member 115 as shown in FIG. 38C. Nevertheless, the method of FIG. 38A has a problem of poorer seating comfort under normal riding conditions. The methods of FIGS. 38B and 38C have a problem of poorer workability in mounting the child seat 100. The method of FIG. 38B in particular has the problem that floor vibrations can be transmitted to the child seat 100 with a deterioration in the riding comfort of the child.
It is thus an object of the present invention to provide a car seat which solves the conventional problems mentioned above and surely suppress the forward movement of the passenger in case of an abrupt vehicle deceleration without deteriorating the seating comfort, yet having a simple low-cost configuration.
Another object is to provide a car seat which provides the foregoing effect irrespective of the seating position or body size of the passenger.
Another object is to provide a car seat which prevents a forward swing of a child seat to secure child's safety sufficiently when the child seat is installed by employing the fixing method of ISO system.